Magnetic tunneling junction devices, memories, electronic systems, and memory systems, and methods of fabricating the same

ABSTRACT

Provided is a magnetic tunneling junction device including a fixed magnetic structure; a free magnetic structure; and a tunnel barrier between the fixed magnetic structure and the free magnetic structure, at least one of the fixed magnetic structure and the free magnetic structure including a perpendicular magnetization preserving layer, a magnetic layer between the perpendicular magnetization preserving layer and the tunnel barrier, and a perpendicular magnetization inducing layer between the perpendicular magnetization preserving layer and the magnetic layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This U.S. non-provisional patent application claims priority under 35U.S.C. §119 to Korean Patent Application Nos. 10-2011-0024429 and10-2011-0074500, filed on Mar. 18, 2011 and Jul. 27, 2011, respectively,in the Korean Intellectual Property Office, the entire contents of whichare hereby incorporated by reference.

BACKGROUND

Embodiments of inventive concepts relate generally to semiconductormemory devices. For example, embodiments of inventive concepts relate tosemiconductor memory devices including magnetic tunneling junction (MTJ)devices, memories, electronic systems, and memory systems and methods offabricating the same.

With increasing use of portable computing devices and wirelesscommunication devices, memory devices may require higher density, lowerpower, and/or nonvolatile properties. Magnetic memory devices may beable to satisfy the aforementioned technical requirements.

An example data storing mechanism for a magnetic memory device is atunnel magneto resistance (TMR) effect of an MTJ. For example, amagnetic memory device with an MTJ have been developed such that an MTJmay have a TMR ratio of several hundred to several thousand percent.However, as pattern dimensions are reduced, it may become more difficultto provide a thermally stable MTJ.

SUMMARY

Example embodiments of inventive concepts provide magnetic memorydevices having improved thermal stability.

Other example embodiments of inventive concepts provide methods offabricating a magnetic memory device having improved thermal stability.

According to example embodiments of inventive concepts, a magnetictunneling junction device may include a fixed magnetic structure; a freemagnetic structure; and a tunnel barrier between the fixed magneticstructure and the free magnetic structure, at least one of the fixedmagnetic structure and the free magnetic structure including aperpendicular magnetization preserving layer, a magnetic layer betweenthe perpendicular magnetization preserving layer and the tunnel barrier,and a perpendicular magnetization inducing layer between theperpendicular magnetization preserving layer and the magnetic layer.

In example embodiments, the magnetic layer is made of a ferromagneticmaterial.

In example embodiments, the ferromagnetic material is at least one ofCoFeB, CoFe, NiFe, CoFePt, CoFePd, CoFeCr, CoFeTb, CoFeGd or CoFeNi.

In example embodiments, the magnetic layer has a thickness in a range ofabout 1 angstrom to about 30 angstroms.

In example embodiments, the magnetic layer has a thickness in a range ofabout 3 angstroms to about 17 angstroms.

In example embodiments, the perpendicular magnetization inducing layeris in direct contact with the magnetic layer.

In example embodiments, the perpendicular magnetization inducing layerincludes at least one of Ta, Ti, U, Ba, Zr, Al, Sr, Hf, La, Ce, Sm, Mg,Th, Ca, Sc, or Y.

In example embodiments, the perpendicular magnetization inducing layerhas an electrical resistivity higher than the magnetic layer or theperpendicular magnetization preserving layer.

In example embodiments, the perpendicular magnetization inducing layerhas a thickness less than the magnetic layer or the perpendicularmagnetization preserving layer.

In example embodiments, the perpendicular magnetization preserving layerhas an electrical resistivity lower than the perpendicular magnetizationinducing layer.

In example embodiments, the perpendicular magnetization preserving layeris formed of at least one noble metal or copper.

In example embodiments, the at least one noble metal includes ruthenium(Ru), rhodium (Rh), palladium (Pd), silver (Ag), osmium (Os), iridium(Ir), platinum (Pt), or gold (Au).

In example embodiments, the magnetic tunneling junction device furtherincludes a substrate; wherein the fixed magnetic structure is a lowerstructure closer to the substrate and the wherein the free magneticstructure is an upper structure further from the substrate.

In example embodiments, the magnetic tunneling junction device furtherincludes a substrate; wherein the free magnetic structure is a lowerstructure closer to the substrate and the wherein the fixed magneticstructure is an upper structure further from the substrate.

According to example embodiments of inventive concepts, an electronicdevice may include a bus; a wireless interface configured to transmitdata to or receive data from a wireless communication network connectedto the bus; an I/O device connected to the bus; a controller connectedto the bus; and a memory including a semiconductor device including amagnetic tunneling junction device, connected to the bus, configured tostore a command code to be used by the controller or user data.

According to example embodiments of inventive concepts, a memory systemmay include a memory device including a semiconductor device including amagnetic tunneling junction device, for storing data; and a memorycontroller configured to control the memory device to read data storedin the memory device or to write data into the memory device in responseto a read/write request of a host.

According to example embodiments of inventive concepts, a magnetictunneling junction device may include a fixed magnetic structure; a freemagnetic structure; and a tunnel barrier between the fixed magneticstructure and the free magnetic structure, at least one of the fixedmagnetic structure and the free magnetic structure including aperpendicular magnetization preserving layer, a magnetic layer betweenthe perpendicular magnetization preserving layer and the tunnel barrier,and a perpendicular magnetization inducing layer between theperpendicular magnetization preserving layer and the magnetic layer;wherein the magnetic layer has an oxygen affinity less than theperpendicular magnetization inducing layer.

In example embodiments, the perpendicular magnetization preserving layerhas an oxygen affinity less than the perpendicular magnetizationinducing layer.

In example embodiments, the perpendicular magnetization inducing layeris an oxygen-containing material.

In example embodiments, the perpendicular magnetization inducing layeris a metal oxide.

In example embodiments, the metal oxide is at least one of magnesiumoxide, tantalum oxide, titanium oxide, aluminum oxide, magnesium zincoxide, hafnium oxide, or magnesium boron oxide.

In example embodiments, the perpendicular magnetization preserving layeris formed of at least one of material having an electrical resistivitylower than tantalum or titanium.

According to example embodiments of inventive concepts, a magnetictunneling junction device may include a first structure including apinned layer; a second structure including a free layer; and a tunnelbarrier between the first and second structures, the second structureincluding a magnetic layer; a perpendicular magnetization inducing layeron the magnetic layer, a perpendicular magnetization preserving layer onthe perpendicular magnetization inducing layer, a capping layer on theperpendicular magnetization preserving layer.

In example embodiments, the magnetic layer has an oxygen affinity lessthan the perpendicular magnetization inducing layer.

In example embodiments, the perpendicular magnetization preserving layerhas an oxygen affinity less than the perpendicular magnetizationinducing layer.

In example embodiments, the perpendicular magnetization inducing layeris an oxygen-containing material.

In example embodiments, the perpendicular magnetization inducing layeris a metal oxide.

In example embodiments, the metal oxide is at least one of magnesiumoxide, tantalum oxide, titanium oxide, aluminum oxide, magnesium zincoxide, hafnium oxide, or magnesium boron oxide.

In example embodiments, the perpendicular magnetization inducing layerhas a thickness less than the magnetic layer or the perpendicularmagnetization preserving layer.

According to example embodiments of inventive concepts, a method offabricating a magnetic device may include forming a magnetic layer;forming a perpendicular magnetization inducing layer on the magneticlayer; forming a perpendicular magnetization preserving layer on theperpendicular magnetization inducing layer; oxidizing the perpendicularmagnetization preserving layer; and annealing the oxidized perpendicularmagnetization preserving layer to diffuse oxygen from the perpendicularmagnetization preserving layer to the perpendicular magnetizationinducing layer.

In example embodiments, the method further includes forming a cappinglayer on the oxidized perpendicular magnetization preserving layer.

In example embodiments, oxidizing the perpendicular magnetizationpreserving layer includes supplying a gas containing oxygen at atemperature of a 0-500° C.

In example embodiments, the gas containing oxygen further includesozone.

In example embodiments, oxidizing the perpendicular magnetizationpreserving layer includes forming a stoichiometric oxide layer.

In example embodiments, oxidizing the perpendicular magnetizationpreserving layer includes nonhomogeneously distributing oxygen atoms inthe perpendicular magnetization preserving layer.

In example embodiments, annealing the oxidized perpendicularmagnetization preserving layer includes a thermal treatment includingsupplying at least one of nitrogen or an inert gas as an ambient gas.

In example embodiments, the magnetic layer has an oxygen affinity lessthan the perpendicular magnetization inducing layer.

In example embodiments, the perpendicular magnetization preserving layerhas an oxygen affinity less than the perpendicular magnetizationinducing layer.

In example embodiments, the magnetic layer is made of a ferromagneticmaterial.

In example embodiments, the ferromagnetic material is at least one ofCoFeB, CoFe, NiFe, CoFePt, CoFePd, CoFeCr, CoFeTb, CoFeGd or CoFeNi.

In example embodiments, the magnetic layer has a thickness in a range ofabout 1 angstrom to about 30 angstroms.

In example embodiments, the magnetic layer has a thickness in a range ofabout 3 angstroms to about 17 angstroms

In example embodiments, the perpendicular magnetization inducing layeris in direct contact with the magnetic layer.

In example embodiments, the perpendicular magnetization inducing layeris an oxygen-containing material.

In example embodiments, the perpendicular magnetization inducing layeris a metal oxide.

In example embodiments, the metal oxide is at least one of magnesiumoxide, tantalum oxide, titanium oxide, aluminum oxide, magnesium zincoxide, hafnium oxide, or magnesium boron oxide.

In example embodiments, the perpendicular magnetization inducing layerincludes at least one of Ta, Ti, U, Ba, Zr, Al, Sr, Hf, La, Ce, Sm, Mg,Th, Ca, Sc, or Y.

In example embodiments, the perpendicular magnetization inducing layerhas an electrical resistivity higher than the magnetic layer or theperpendicular magnetization preserving layer.

In example embodiments, the perpendicular magnetization inducing layerhas a thickness less than the magnetic layer or the perpendicularmagnetization preserving layer.

In example embodiments, the perpendicular magnetization preserving layerhas an electrical resistivity lower than the perpendicular magnetizationinducing layer.

In example embodiments, the perpendicular magnetization preserving layeris formed of at least one noble metal or copper.

In example embodiments, the at least one noble metal includes ruthenium(Ru), rhodium (Rh), palladium (Pd), silver (Ag), osmium (Os), iridium(Ir), platinum (Pt), or gold (Au).

In example embodiments, the perpendicular magnetization preserving layeris formed of at least one of material having an electrical resistivitylower than tantalum or titanium.

According to example embodiments of inventive concepts, a method offabricating a magnetic device may include forming a seeding layer;forming a perpendicular magnetization preserving layer on the seedinglayer; oxidizing the perpendicular magnetization preserving layer;forming a perpendicular magnetization inducing layer on the oxidizedperpendicular magnetization preserving layer; forming a magnetic layeron the perpendicular magnetization inducing layer; and annealing theoxidized perpendicular magnetization preserving layer to diffuse oxygenfrom the perpendicular magnetization preserving layer to theperpendicular magnetization inducing layer.

In example embodiments, the magnetic layer has an oxygen affinity lessthan the perpendicular magnetization inducing layer.

In example embodiments, the perpendicular magnetization preserving layerhas an oxygen affinity less than the perpendicular magnetizationinducing layer.

In example embodiments, the magnetic layer is at least one of CoFeB,CoFe, NiFe, CoFePt, CoFePd, CoFeCr, CoFeTb, CoFeGd or CoFeNi.

In example embodiments, the perpendicular magnetization inducing layeris an oxygen-containing material.

In example embodiments, the perpendicular magnetization inducing layeris a metal oxide.

In example embodiments, the metal oxide is at least one of magnesiumoxide, tantalum oxide, titanium oxide, aluminum oxide, magnesium zincoxide, hafnium oxide, or magnesium boron oxide.

In example embodiments, the perpendicular magnetization inducing layerincludes at least one of Ta, Ti, U, Ba, Zr, Al, Sr, Hf, La, Ce, Sm, Mg,Th, Ca, Sc, or Y.

In example embodiments, the perpendicular magnetization inducing layerhas an electrical resistivity higher than the magnetic layer or theperpendicular magnetization preserving layer.

In example embodiments, the perpendicular magnetization preserving layerincludes ruthenium (Ru), rhodium (Rh), palladium (Pd), silver (Ag),osmium (Os), iridium (Ir), platinum (Pt), or gold (Au).

In example embodiments, the perpendicular magnetization preserving layeris formed of at least one of material having an electrical resistivitylower than tantalum or titanium.

BRIEF DESCRIPTION OF THE DRAWINGS

Example embodiments will be more clearly understood from the followingbrief description taken in conjunction with the accompanying drawings.The accompanying drawings represent non-limiting, example embodiments asdescribed herein.

FIG. 1 is a schematic circuit diagram of a unit cell of a magneticmemory device according to example embodiments of inventive concepts;

FIGS. 2 through 6 are circuit diagrams exemplarily illustratingselection devices according to example embodiments of inventiveconcepts;

FIG. 7 is a diagram schematically illustrating a first type of MTJaccording to example embodiments of inventive concepts;

FIG. 8 is a diagram schematically illustrating a second type of MTJaccording to example embodiments of inventive concepts;

FIG. 9 is a perspective view exemplarily illustrating an extrinsicperpendicular magnetization structure according to example embodimentsof inventive concepts;

FIGS. 10A and 10B are graphs illustrating some aspects of the extrinsicperpendicular magnetization structure;

FIG. 11 is a graph illustrating other aspects of the extrinsicperpendicular magnetization structure;

FIG. 12 is a graph illustrating still other aspects of the extrinsicperpendicular magnetization structure;

FIG. 13 is a table showing an exemplary classification of lower andupper structures according to example embodiments of inventive concepts;

FIGS. 14 through 17 are sectional views of the lower structuresaccording to example embodiments of inventive concepts;

FIGS. 18 through 21 are sectional views of the upper structuresaccording to example embodiments of inventive concepts;

FIG. 22 is a table showing an exemplary classification of the first typeof MTJ according to example embodiments of inventive concepts;

FIGS. 23 through 25 are sectional views exemplarily illustrating thefirst type of MTJ according to example embodiments of inventiveconcepts;

FIG. 26 is a table showing an exemplary classification of the secondtype of MTJ according to example embodiments of inventive concepts;

FIGS. 27 through 29 are sectional views exemplarily illustrating thesecond type of MTJ according to example embodiments of inventiveconcepts;

FIG. 30 is a schematic circuit diagram of a unit cell of a magneticmemory device according to modified embodiments of inventive concepts;

FIG. 31 is a flowchart exemplarily illustrating a method of fabricatinga MTJ according to some example embodiments of inventive concepts;

FIG. 32 is a graph illustrating some aspects of the MTJ fabricated bythe method of FIG. 31;

FIG. 33 is a flowchart exemplarily illustrating a method of fabricatinga MTJ according to other example embodiments of inventive concepts;

FIG. 34 is a graph illustrating some aspects of the MTJ fabricated bythe method of FIG. 33;

FIG. 35 is an experimental graph exemplarily showing some magneticproperties of MTJ according to example embodiments of inventiveconcepts;

FIG. 36 is an experimental graph exemplarily showing other magneticproperties of MTJ according to example embodiments of inventiveconcepts; and

FIGS. 37 and 38 are schematic block diagrams schematically illustratingelectronic devices including a semiconductor device according to exampleembodiments of inventive concepts.

It should be noted that these figures are intended to illustrate thegeneral characteristics of methods, structure and/or materials utilizedin certain example embodiments and to supplement the written descriptionprovided below. These drawings are not, however, to scale and may notprecisely reflect the precise structural or performance characteristicsof any given embodiment, and should not be interpreted as defining orlimiting the range of values or properties encompassed by exampleembodiments. For example, the relative thicknesses and positioning ofmolecules, layers, regions and/or structural elements may be reduced orexaggerated for clarity. The use of similar or identical referencenumbers in the various drawings is intended to indicate the presence ofa similar or identical element or feature.

DETAILED DESCRIPTION

Example embodiments of inventive concepts will now be described morefully with reference to the accompanying drawings, in which exampleembodiments are shown. Example embodiments of inventive concepts may,however, be embodied in many different forms and should not be construedas being limited to example embodiments set forth herein; rather, theseexample embodiments are provided so that this disclosure will bethorough and complete, and will fully convey the concept of exampleembodiments to those of ordinary skill in the art. In the drawings, thethicknesses of layers and regions are exaggerated for clarity. Likereference numerals in the drawings denote like elements, and thus theirdescription will be omitted.

It will be understood that when an element is referred to as being“connected” or “coupled” to another element, it can be directlyconnected or coupled to the other element or intervening elements may bepresent. In contrast, when an element is referred to as being “directlyconnected” or “directly coupled” to another element, there are nointervening elements present. Like numbers indicate like elementsthroughout. As used herein the term “and/or” includes any and allcombinations of one or more of the associated listed items. Other wordsused to describe the relationship between elements or layers should beinterpreted in a like fashion (e.g., “between” versus “directlybetween,” “adjacent” versus “directly adjacent,” “on” versus “directlyon”).

It will be understood that, although the terms “first”, “second”, etc.may be used herein to describe various elements, components, regions,layers and/or sections, these elements, components, regions, layersand/or sections should not be limited by these terms. These terms areonly used to distinguish one element, component, region, layer orsection from another element, component, region, layer or section. Thus,a first element, component, region, layer or section discussed belowcould be termed a second element, component, region, layer or sectionwithout departing from the teachings of example embodiments.

Spatially relative terms, such as “beneath,” “below,” “lower,” “above,”“upper” and the like, may be used herein for ease of description todescribe one element or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if the device in thefigures is turned over, elements described as “below” or “beneath” otherelements or features would then be oriented “above” the other elementsor features. Thus, the exemplary term “below” can encompass both anorientation of above and below. The device may be otherwise oriented(rotated 90 degrees or at other orientations) and the spatially relativedescriptors used herein interpreted accordingly.

The terminology used herein is for the purpose of describing particularexample embodiments only and is not intended to be limiting of exampleembodiments. As used herein, the singular forms “a,” “an” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“comprises”, “comprising”, “includes” and/or “including,” if usedherein, specify the presence of stated features, integers, steps,operations, elements and/or components, but do not preclude the presenceor addition of one or more other features, integers, steps, operations,elements, components and/or groups thereof.

Example embodiments of inventive concepts are described herein withreference to cross-sectional illustrations that are schematicillustrations of idealized embodiments (and intermediate structures) ofexample embodiments. As such, variations from the shapes of theillustrations as a result, for example, of manufacturing techniquesand/or tolerances, are to be expected. Thus, example embodiments ofinventive concepts should not be construed as limited to the particularshapes of regions illustrated herein but are to include deviations inshapes that result, for example, from manufacturing. For example, animplanted region illustrated as a rectangle may have rounded or curvedfeatures and/or a gradient of implant concentration at its edges ratherthan a binary change from implanted to non-implanted region. Likewise, aburied region formed by implantation may result in some implantation inthe region between the buried region and the surface through which theimplantation takes place. Thus, the regions illustrated in the figuresare schematic in nature and their shapes are not intended to illustratethe actual shape of a region of a device and are not intended to limitthe scope of example embodiments.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which example embodiments of inventiveconcepts belong. It will be further understood that terms, such as thosedefined in commonly-used dictionaries, should be interpreted as having ameaning that is consistent with their meaning in the context of therelevant art and will not be interpreted in an idealized or overlyformal sense unless expressly so defined herein.

FIG. 1 is a circuit diagram exemplarily illustrating a unit cell ofmagnetic memory devices according to example embodiments of inventiveconcepts.

Referring to FIG. 1, a unit cell 100 may be disposed between first andsecond interconnection lines 10 and 20 crossing each other. The unitcell 100 may be connected in series to the first and secondinterconnection lines 10 and 20. The unit cell 100 may include aselection element 30 and a magnetic tunnel junction MTJ. The selectionelement 30 and the magnetic tunnel junction MTJ may be electricallyconnected in series to each other. In some example embodiments, one ofthe first and second interconnection lines 10 and 20 may be used as aword line, and the other may be used as a bit line.

The selection element 30 may be configured to selectively control anelectric current passing through the magnetic tunnel junction MTJ. Forexample, as shown in FIGS. 2 through 6, the selection element 30 may beone of a diode, a pnp bipolar transistor, an npn bipolar transistor, anNMOS field effect transistor (FET), and a PMOS FET. In the case that theselection element 30 is a three-terminal switching device, such as abipolar transistor and/or MOSFET, an additional interconnection line(not shown) may be connected to the selection element 30.

The magnetic tunnel junction MTJ may include a lower structure 41, anupper structure 42, and a tunnel barrier 50 therebetween. Each of thelower and upper structures 41 and 42 may include at least one magneticlayer, which is formed of a magnetic material.

One of the magnetic layers may be configured to have a fixedmagnetization direction, which is not changed by an external magneticfield generated under usual circumstances. Hereinafter, for conveniencein description, a term ‘pinned layer PL’ will be used to represent themagnetic layer having the fixed magnetization property. By contrast, theother of the magnetic layers may be configured to have a magnetizationdirection being switchable by an external magnetic field appliedthereto. Hereinafter, a term ‘free layer FRL’ will be used to representthe magnetic layer having the switchable magnetization property. Thatis, as shown in FIGS. 7 and 8, the magnetic tunnel junction MTJ mayinclude at least one free layer FRL and at least one pinned layer PL,which are separated by the tunnel barrier 50.

Electrical resistance of the magnetic tunnel junction MTJ may besensitive to a relative orientation of magnetization directions of thefree and pinned layers FRL and PL. For example, the electricalresistance of the magnetic tunnel junction MTJ may be far greater whenthe relative orientation is antiparallel than when parallel. This meansthat the electrical resistance of the magnetic tunnel junction MTJ maybe controlled by changing the magnetization direction of the free layerFRL. The magnetic memory devices according to example embodiments ofinventive concepts may be realized based on this data storing mechanism.

As shown in FIGS. 7 and 8, the lower and upper structures 41 and 42 ofthe magnetic tunnel junction MTJ may be sequentially formed on asubstrate SUB. In example embodiments, according to a relativeconfiguration between the free layer FRL and the substrate SUB or aforming order of the free layer FRL and the pinned layer PL, themagnetic tunnel junction MTJ may be, for example, classified into twotypes: (a) a first type of magnetic tunnel junction MTJ1 configured insuch a way that the lower and upper structures 41 and 42 include thepinned layer PL and the free layer FRL, respectively, as shown in FIG.7, and (b) a second type of magnetic tunnel junction MTJ2 configured insuch a way that the lower and upper structures 41 and 42 include thefree layer FRL and the pinned layer PL, respectively, as shown in FIG.8.

FIG. 9 is a perspective view exemplarily illustrating an extrinsicperpendicular magnetization structure, which may be provided as a partof a MTJ according to example embodiments of inventive concepts, andFIGS. 10A and 10B are graphs illustrating some aspects of the extrinsicperpendicular magnetization structure.

According to some aspects of inventive concepts, at least one of thelower structure 41 and the upper structure 42 may configure an extrinsicperpendicular magnetization structure EPMS. In some example embodiments,the extrinsic perpendicular magnetization structure EPMS may include amagnetic layer MGL, a perpendicular magnetization preserving layer PMP,and/or a perpendicular magnetization inducing layer PMI interposedbetween the magnetic layer MGL and the perpendicular magnetizationpreserving layer PMP, as shown in FIG. 9. The magnetic layer MGL of theextrinsic perpendicular magnetization structure EPMS may be used as themagnetic layer included in the lower structure 41 and the upperstructure 42. In other words, the free or pinned layer FRL or PL may bethe magnetic layer MGL of the extrinsic perpendicular magnetizationstructure EPMS.

The magnetic layer MGL may include a ferromagnetic material. Forexample, the magnetic layer MGL may be formed of at least one of CoFeB,CoFe, NiFe, CoFePt, CoFePd, CoFeCr, CoFeTb, CoFeGd or CoFeNi. Inaddition, the magnetic layer MGL may be provided in a form of thinpattern, whose vertical thickness is far smaller than horizontal lengthsthereof. For example, a thickness of the magnetic layer MGL may be in arange of about 1 angstrom to about 30 angstroms. In more specificexample embodiments, the thickness of the magnetic layer MGL may be in arange of about 3 angstroms to about 17 angstroms. In exampleembodiments, owing to magnetic anisotropy caused by the geometricalshape of the magnetic layer MGL, the magnetic layer MGL may have amagnetization direction confined to a plane (e.g., xy-plane) parallel toa top surface thereof. Hereinafter, this magnetic property of themagnetic layer MGL will be called ‘intrinsic horizontal magnetizationproperty’. That is, the magnetic layer MGL may be an intrinsichorizontal magnetic layer having the intrinsic horizontal magnetizationproperty.

In modified example embodiments of inventive concepts, the magneticlayer MGL may be an intrinsic perpendicular magnetic (IPM) layer havingan intrinsic perpendicular magnetization property. That is, the magneticlayer MGL may have a magnetization direction that is spontaneouslyoriented perpendicular to the xy-plane or the top surface thereof. Forexample, the magnetic layer MGL may include at least one of a) CoFeTb,in which the relative content of Tb is 10% or more, b) CoFeGd, in whichthe relative content of Gd is 10% or more, c) CoFeDy, d) FePt with theL1₀ structure, e) FePd with the L1₀ structure, f) CoPd with the L1₀structure, g) CoPt with the L1₀ structure, h) CoPt with the hexagonalclose packing (HCP) structure, i) alloys containing at least one ofmaterials presented in items of a) to h), or j) a multi-layeredstructure including magnetic and non-magnetic layers alternatinglystacked. The multi-layered structure including the alternatingly-stackedmagnetic and non-magnetic layers may include at least one of (Co/Pt)n,(CoFe/Pt)n, (CoFe/Pd)n, (CoP)n, (Co/Ni)n, (CoNi/Pt)n, (CoCr/Pt)n, or(CoCr/Pd)n, where the subscript n denotes the stacking number.

The perpendicular magnetization inducing layer PMI may be formed to bein direct contact with the magnetic layer MGL, and this directlycontacting configuration enables to change a magnetization direction ofthe magnetic layer MGL from parallel to perpendicular to a top plane ofthe magnetic layer MGL. That is, the perpendicular magnetizationinducing layer PMI may serve as an external factor for the magneticlayer MGL to have the perpendicular magnetization property. In thissense, the perpendicular magnetization inducing layer PMI and themagnetic layer MGL being in contact with each other may constitute amagnetic structure with an extrinsic perpendicular magnetizationproperty (e.g., the extrinsic perpendicular magnetization structure).Hereinafter, the magnetic layer MGL in the extrinsic perpendicularmagnetization structure may be called “an extrinsic perpendicularmagnetic (EPM) layer”.

The perpendicular magnetization inducing layer PMI may be anoxygen-containing material. In some example embodiments, theperpendicular magnetization inducing layer PMI may be at least one ofmetal oxides. For example, the perpendicular magnetization inducinglayer PMI may be at least one of magnesium oxide, tantalum oxide,titanium oxide, aluminum oxide, magnesium zinc oxide, hafnium oxide, ormagnesium boron oxide. In example embodiments, the perpendicularmagnetization inducing layer PMI may have electrical resistivity higherthan the magnetic layer MGL or the perpendicular magnetizationpreserving layer PMP. In example embodiments, an electric resistance ofthe magnetic tunnel junction MTJ may be strongly dependent on theelectrical resistivity of the perpendicular magnetization inducing layerPMI. In order to reduce this dependency, the perpendicular magnetizationinducing layer PMI may be formed to be thin. For example, theperpendicular magnetization inducing layer PMI may be formed to have athickness less than the magnetic layer MGL or the perpendicularmagnetization preserving layer PMP.

The perpendicular magnetization preserving layer PMP may be formed of amaterial having resistivity lower than the perpendicular magnetizationinducing layer PMI. For example, the perpendicular magnetizationpreserving layer PMP may be formed of at least one of noble metals (suchas, ruthenium (Ru), rhodium (Rh), palladium (Pd), silver (Ag), osmium(Os), iridium (Ir), platinum (Pt), or gold (Au)) or copper. According tosome example embodiments of inventive concepts, the perpendicularmagnetization preserving layer PMP may be formed of at least one ofmaterials having resistivity lower than tantalum or titanium.

In addition, according to some aspects of inventive concepts, a portionof the perpendicular magnetization preserving layer PMP, which is incontact with the perpendicular magnetization inducing layer PMI, may beformed of a material hardly reacting with oxygen atoms. The noble metalsor copper described above may be selected as a material satisfying thisrequirement for the perpendicular magnetization preserving layer PMP. Insome example embodiments, the perpendicular magnetization preservinglayer PMP may be formed of a material hardly reacting with oxygen atoms,even during subsequent process steps or under normal operatingconditions.

For example, as shown in FIG. 10A, the perpendicular magnetizationpreserving layer PMP may be a material having an oxygen affinity lessthan metallic elements constituting the perpendicular magnetizationinducing layer PMI. In example embodiments, the oxygen affinity may berepresented by the standard enthalpy of reaction for the formation ofmetal oxide (ΔH⁰ _(f) [kJ/mole Oxygen]), as shown in FIG. 10B. In someexample embodiments, the standard enthalpy of reaction ΔH⁰ _(f) of themetallic elements constituting the perpendicular magnetization inducinglayer PMI may be less than about −500 [kJ/mole Oxygen], and the standardenthalpy of reaction ΔH⁰ _(f) of the perpendicular magnetizationpreserving layer PMP may be greater than −300 [kJ/mole Oxygen]. That is,the standard enthalpy of reaction may be greater for the metallicelements constituting the perpendicular magnetization inducing layer PMIthan for the perpendicular magnetization preserving layer PMP, in termsof the absolute value. In some example embodiments, the metallicelements constituting the perpendicular magnetization inducing layer PMImay be at least one of Ta, Ti, U, Ba, Zr, Al, Sr, Hf, La, Ce, Sm, Mg,Th, Ca, Sc, or Y, and the perpendicular magnetization preserving layerPMP may include at least one of Au, Ag, Pt, Pd, Rh, Ru, Cu, Re, or Pb.As shown in FIG. 10A or 10B, the magnetic layer MGL may be formed of amaterial having an oxygen affinity less than the metallic elementsconstituting the perpendicular magnetization inducing layer PMI andgreater than the perpendicular magnetization preserving layer PMP. Inexample embodiments, chemical reactivity with oxygen can be representedby various physical quantities. For example, physical quantities, suchas an oxidation potential or a free energy in oxidation, can be used toquantitatively represent the chemical reactivity with oxygen, instead ofthe oxygen affinity or the standard enthalpy of reaction.

FIG. 11 is a graph illustrating other aspects of the extrinsicperpendicular magnetization structure. Referring to FIG. 11, theextrinsic perpendicular magnetization property may result from achemical combination of atoms in the magnetic layer MGL and oxygen atomsin the perpendicular magnetization inducing layer PMI. In exampleembodiments, as shown in FIG. 11, a transition region TR, whose oxygencontent is higher than the magnetic layer MGL and lower than theperpendicular magnetization inducing layer PMI, may be formed betweenthe magnetic layer MGL and the perpendicular magnetization inducinglayer PMI. In some example embodiments, there is no reason that theoxygen content should be linear in the transition region TR. Forexample, in the transition region TR, the oxygen content may varymonotonically within a specific envelope ENV, as shown in FIG. 11.

Alternatively, the perpendicular magnetization preserving layer PMP maybe formed of a material hardly reacting with oxygen atoms, even duringsubsequent processes or under normal operating conditions. In someexample embodiments, as shown in FIG. 11, the perpendicularmagnetization inducing layer PMI may be formed to have finite oxygencontent, and the perpendicular magnetization preserving layer PMP may beformed to have a substantially infinitesimal oxygen content. In someexample embodiments, the oxygen content may vary abruptly at aninterface between the perpendicular magnetization inducing layer PMI andthe perpendicular magnetization preserving layer PMP. That is, anabsolute value of gradient of the oxygen content may be greater at theinterface between the perpendicular magnetization inducing layer PMI andthe perpendicular magnetization preserving layer PMP than at thetransition region TR.

In other example embodiments, the transition region TR may be formed inthe whole region of the perpendicular magnetization inducing layer PMI.For example, in the graph of FIG. 11, a z-directional gradient of oxygencontent may have a finite non-vanishing value in the whole region of theperpendicular magnetization inducing layer PMI or between the magneticlayer MGL and the perpendicular magnetization preserving layer PMP. Insome example embodiments, the oxygen content of the perpendicularmagnetization inducing layer PMI may be greater at a region adjacent tothe perpendicular magnetization preserving layer PMP than at otherregion adjacent to the magnetic layer MGL.

FIG. 12 is a graph illustrating still other aspects of an extrinsicperpendicular magnetization structure.

The formation of the magnetic memory device may further include processsteps (for example, at least one thermal treatment step, a wiring step,and so forth), which will be performed after forming the perpendicularmagnetization inducing layer PMI and the perpendicular magnetizationpreserving layer PMP. As shown in FIG. 12, an thermal energy, which maybe generated during these subsequent process steps or by user's normaloperation, may be supplied to the perpendicular magnetization inducinglayer PMI. This thermal energy may dissociate oxygen atoms from theperpendicular magnetization inducing layer PMI.

However, in the case that the perpendicular magnetization preservinglayer PMP having the low oxygen affinity is formed to cover theperpendicular magnetization inducing layer PMI, it is possible toprevent the dissociated oxygen atoms from diffusing away from theperpendicular magnetization inducing layer PMI. For instance, if thethermal energy is not supplied from outside the magnetic tunnel junctionMTJ, the dissociated oxygen atoms may be restored to its chemicallystable state. Here, in the case that, as the afore-describedembodiments, the perpendicular magnetization preserving layer PMP isformed of a material having a low oxygen affinity, the dissociatedoxygen atoms may be recombined with metal elements constituting theperpendicular magnetization inducing layer PMI, not the perpendicularmagnetization preserving layer PMP. That is, the perpendicularmagnetization inducing layer PMI may be restored to its original statebefore the supply of the thermal energy.

As described with reference to FIG. 1, each of the lower and upperstructures 41 and 42 may include a magnetic layer, and according to itsfunction the magnetic layer may be classified into the free layer FRL orthe pinned layer PL, as described with reference to FIGS. 7 and 8. Inaddition, when an external inducing element (e.g., the perpendicularmagnetization inducing layer PMI) is provided, the magnetic layer mayserve as a part of the extrinsic perpendicular magnetization structureEPMS, as described with reference to FIG. 9.

In some example embodiments, the IPM layer having the afore-describedintrinsic perpendicular magnetization property may be used as one of themagnetic layers included in the lower and upper structures 41 and 42. Inother words, one of the magnetic layers included in the lower and upperstructures 41 and 42 is configured to have the perpendicularmagnetization property, even when there is no external inducing element,such as the perpendicular magnetization inducing layer PMI of theextrinsic perpendicular magnetization structure EPMS. For example, theIPM layer may include one of a) CoFeTb, in which the relative content ofTb is 10% or more, b) CoFeGd, in which the relative content of Gd is 10%or more, c) CoFeDy, d) FePt with the L1₀ structure, e) FePd with the L1₀structure, f) CoPd with the L1₀ structure, g) CoPt with the L1₀structure, h) CoPt with the hexagonal close packing (HCP) structure, i)alloys containing at least one of materials presented in items of a) toh), or j) a multi-layered structure including magnetic and non-magneticlayers alternatingly stacked. The multi-layered structure including thealternatingly-stacked magnetic and non-magnetic layers may include atleast one of (Co/Pt)n, (CoFe/Pt)n, (CoFe/Pd)n, (CoP)n, (Co/Ni)n,(CoNi/Pt)n, (CoCr/Pt)n, or (CoCr/Pd)n, where the subscript n denotes thestacking number.

In summary, each of the magnetic layers constituting the magnetic tunneljunction MTJ can be classified in various manners, according to itsposition, function and origin of perpendicularity in magnetizationdirection, as exemplarily shown in FIG. 13. FIGS. 14 through 21 aresectional views exemplarily showing the lower or upper structure 41 or42 including a magnetic layer according to this classification.

Referring to FIG. 13, according to positional classification, each ofthe magnetic layers in the magnetic tunnel junction MTJ may be amagnetic layer 210 or 215 for the lower structure 41, as shown in FIGS.14 through 17, or a magnetic layer 310 or 315 for the upper structure42, as shown in FIGS. 18 through 21. That is, the lower structure 41 maybe one of first to fourth lower structures 201, 202, 203 and 204 shownin FIGS. 14 through 17, and the upper structure 42 may be one of firstto fourth upper structures 301, 302, 303 and 304 shown in FIGS. 18through 21.

In addition, according to functional classification, the magnetic layer210, 215, 310 and 315 may be used as the free layer FRL having aswitchable magnetization property, as exemplarily illustrated in FIGS.14, 16, 18 and 20, or as the pinned layer PL having a fixedmagnetization property, as exemplarily illustrated in FIGS. 15, 17, 19and 21. That is, the first and third lower structures 201 and 203 andthe first and third upper structures 301 and 303 may be configured toinclude the free layer FRL, and the second and fourth lower structures202 and 204 and the second and fourth upper structures 302 and 304 maybe configured to include the pinned layer PL.

Referring to FIGS. 15, 17, 19 and 21, in the case that the magneticlayer 210, 215, 310 or 315 is used as the pinned layer PL, the lower orupper structures 41 or 42 may further include a pinning layer 240 or 340fixing the magnetization direction of the magnetic layer 210, 215, 310or 315. That is, the second and fourth lower structures 202 and 204 andthe second and fourth upper structures 302 and 304 may further includethe pinning layer 240 or 340.

According to some example embodiments, the pinning layer 240 or 340 maybe configured to have a synthetic antiferromagnetic (SAF) structure. Forexample, the pinning layer 240 or 340 may be configured to include apair of the intrinsic horizontal magnetic layers and an exchangecoupling layer interposed therebetween. The exchange coupling layer maybe formed of one of noble metals.

According to other example embodiments, as exemplarily shown in FIGS. 15and 19, the pinning layer 240 or 340 may be configured to have amulti-layered structure including a first pinning layer 241 or 341 and asecond pinning layer 242 or 342. In some example embodiments, the firstpinning layer 241 or 341 may be configured to have the afore-mentionedSAF structure, and the second pinning layer 242 or 342 may be theafore-described IPM layer.

Referring back to FIG. 13, according to classification based on theorigin of the perpendicular magnetization, the magnetic layer serving asthe free layer FRL or the pinned layer PL may be an extrinsicperpendicular magnetic (EPM) layer 210 or 310, whose perpendicularmagnetization has its origin in an external factor, or an IPM layer 215or 315, whose perpendicular magnetization has its origin in an internalfactor. The EPM layer 210 or 310 may be formed to be in direct contactwith a perpendicular magnetization inducing (PMI) layer 220 or 320causing the perpendicular magnetization thereof, as shown in FIGS. 14,15, 18 and 19. The PMI layer 220 or 320 may be configured to have thesame technical features as the perpendicular magnetization inducinglayer PMI described with reference to FIG. 9. Accordingly, the EPM layer210 or 310 and the PMI layer 220 or 320 may constitute the extrinsicperpendicular magnetization structure EPMS described with reference toFIG. 9.

In example embodiments where the magnetic layer is used as the EPM layer210 of the lower structure 41, a perpendicular magnetization preserving(PMP) layer 230 may be disposed below the EPM layer 210 and the PMIlayer 220 may be interposed between the PMP layer 230 and the EPM layer210, as shown in FIGS. 14 and 15. That is, the PMI layer 220 and the EPMlayer 210 may be sequentially stacked on the PMP layer 230. Furthermore,in the case that the magnetic layer is uses as the EPM layer 310 of theupper structure 42, a PMP layer 330 may be disposed on the EPM layer 310and the PMI layer 320 may be interposed between the EPM layer 310 andthe PMP layer 330 as shown in FIGS. 18 and 19. That is, the PMI layer320 and the PMP layer 330 may be sequentially stacked on the EPM layer310.

The PMP layer 230 and 330 may be formed of a material hardly reactingwith oxygen atoms. For example, the PMP layer 230 and 330 may be amaterial, whose oxygen affinity is lower than metal atoms contained inthe perpendicular magnetization inducing layer PMI. In some exampleembodiments, the PMP layer 230 and 330 may be formed of a materialhaving the standard enthalpy of reaction of −300 or less [kJ/moleOxygen] and the perpendicular magnetization inducing layer PMI may be acompound containing metal atoms whose standard enthalpy of reaction is−300 or more [kJ/mole Oxygen].

Accordingly, the PMP layer 230 or 330, the EPM layer 210 or 310, and thePMI layer 220 or 320 may constitute the extrinsic perpendicularmagnetization structure EPMS described with reference to FIG. 9. In someexample embodiments, the PMP layer 230 and 330 may be formed of at leastone of noble metals or copper.

As exemplarily shown in FIGS. 15 and 19, in the case that the pinninglayers 240 and 340 include the second pinning layers 242 and 342,respectively, the second pinning layers 242 and 342 may be more adjacentto the PMP layers 230 and 330, respectively, compared with the firstpinning layer 241 and 341. In these example embodiments, the PMP layer230 or 330 may be formed of at least one of materials allowing anexchange coupling between the EPM layer 210 or 310 and the secondpinning layer 242 or 342. In some example embodiments, the EPM layer 210and 310 may be configured to have parallel or antiparallel magnetizationdirection with respect to the second pinning layer 242 and 342,respectively.

The exchange coupling may be realized using some of the noble metalsthat are exemplarily mentioned as a material for the PMP layers 230 and330. For example, the PMP layer 230 or 330 may include at least one ofruthenium (Ru), iridium (Ir), or rhodium (Rh). In other embodiments, thePMP layer 230 and 330 may be formed of at least one of non-magneticmetals, such as, titanium (Ti), tantalum (Ta), or magnesium (Mg), oxidesthereof, or nitrides thereof

As shown in FIGS. 16 and 20, the magnetic layer may be uses as the IPMlayer 215 or 315 in aspects of its origin of perpendicularity and as thefree layer FRL in aspects of its function. According to these exampleembodiments, a lower layer 235 may be disposed below the IPM layer 215or an upper layer 335 may be disposed on the IPM layer 315. The lowerlayer 235 and the upper layer 335 may be formed of at least one ofmetals. For example, the upper layer 335 and the lower layer 235 mayinclude at least one of ruthenium (Ru), tantalum (Ta), palladium (Pd),titanium (Ti), platinum (Pt), silver (Ag), gold (Au), or copper (Cu).

In some example embodiments, the lower layer 235 may serve as a seedlayer for growing the IPM layer 215 thereon. For instance, in the casethat the IPM layer 215 is formed of a material with L10 structure, thelower layer 235 may include a conductive metal nitride layer with thesodium chloride crystal structure (e.g., of titanium nitride, tantalumnitride, chromium nitride, or vanadium nitride). The upper layer 335 mayserve as a capping layer for protecting the IPM layer 315 thereunder.

The first to fourth lower structures 201, 202, 203 and 204 and the firstto fourth upper structures 301, 302, 303 and 304 may be used to realizethe magnetic tunnel junction MTJ according to example embodiments ofinventive concepts described with reference to FIG. 1. In exampleembodiments, the magnetic tunnel junction MTJ may include the lowerstructure 41, the tunnel barrier 50, and the upper structure 42, whichare sequentially stacked, as described with reference to FIG. 1, and bethe first type of magnetic tunnel junction MTJ1 described with referenceto FIG. 7 or the second type of magnetic tunnel junction MTJ2 describedwith reference to FIG. 8.

In other words, as shown in FIG. 22, the first type of magnetic tunneljunction MTJ1 may be configured to have the lower structure 41 includingthe pinned layer PL and the upper structure 42 including the free layerFRL. The lower structure 41 including the pinned layer PL may be thesecond lower structure 202 shown in FIGS. 23 and 24 or the fourth lowerstructure 204 shown in FIG. 25. The upper structure 42 including thefree layer FRL may be the first upper structure 301 shown in FIGS. 23and 25 or the third upper structure 303 shown in FIG. 24.

Alternatively, as shown in FIG. 26, the second type of magnetic tunneljunction MTJ2 may be configured to have the lower structure 41 includingthe free layer FRL and the upper structure 42 including the pinned layerPL. The lower structure 41 including the free layer FRL may be the firstlower structure 201 shown in FIGS. 27 and 28 or the third lowerstructure 203 shown in FIG. 29. The upper structure 42 including thepinned layer PL maybe the second upper structure 302 shown in FIGS. 27and 29 or the fourth upper structure 304 shown in FIG. 28.

FIG. 30 is a schematic circuit diagram of a unit cell of a magneticmemory device according to modified example embodiments of inventiveconcepts.

Referring to FIG. 30, a magnetic tunnel junction MTJ according to thepresent embodiments may further include at least one of a lowerelectrode structure 61 disposed below the lower structure 41 and anupper electrode structure 62 disposed on the upper structure 42. Thelower electrode structure 61 may be disposed between the firstinterconnection line 10 and the lower structure 41 or between theselection element 30 and the lower structure 41, and the upper electrodestructure 62 may be disposed between the second interconnection line 20and the upper structure 42.

In some example embodiments, at least one of the lower and upperelectrode structures 61 and 62 may be configured to have asingle-layered structure. In other example embodiments, at least one ofthe lower and upper electrode structures 61 and 62 may be configured tohave a multi-layered structure. In addition, the lower and upperelectrode structures 61 and 62 may include at least one conductive layer(e.g., of metal). For example, the conductive layer of the upperelectrode structure 62 may be a third capping layer CL3, which will bedescribed with reference to FIGS. 31 and 32, the conductive layer of thelower electrode structure 61 may be a first seed layer SL1, which willbe described with reference to FIGS. 33 and 34. But example embodimentsof inventive concepts need not be limited thereto; for instance, inother modified example embodiments, a magnetic tunnel junction MTJ maybe configured not to include one of the lower and upper electrodestructures 61 and 62.

FIG. 31 is a flowchart exemplarily illustrating a method of fabricatinga MTJ according to some example embodiments of inventive concepts, andFIG. 32 is a graph illustrating some aspects of the MTJ fabricated bythe method of FIG. 31. In example embodiments, FIG. 32 shows a temporalchange in oxygen content in layers constituting the MTJ, and thehorizontal and vertical axes represent the layer and the oxygen content,respectively. In order to reduce complexity in the drawings and toprovide better understanding of example embodiments of inventiveconcepts, FIG. 32 shows together oxygen contents in some steps describedwith reference to FIG. 31.

Referring to FIGS. 31 and 32, a magnetic layer MGL may be formed (inS10). The magnetic layer MGL may be formed of a ferromagnetic materialor the IPM layer.

Thereafter, a first capping layer CL1, for example, a perpendicularmagnetization inducing layer PMI, and a second capping layer CL2, forexample, a perpendicular magnetization preserving layer PMP, may besequentially formed on the magnetic layer MGL (in S20 and S30). Thefirst capping layer CL1 may be formed of a material having an oxygenaffinity greater than the magnetic layer MGL and/or the second cappinglayer CL2. In some example embodiments, the first capping layer CL1 maybe formed of at least one of magnesium, tantalum, titanium, aluminum,magnesium zinc, hafnium, or magnesium boron, and the second cappinglayer CL2 may be formed of at least one of noble metals (e.g., ruthenium(Ru), rhodium (Rh), palladium (Pd), silver (Ag), osmium (Os), iridium(Ir), platinum (Pt), or gold (Au)) or copper. In some exampleembodiments, the first capping layer CL1 may be formed to have athickness one to three times greater than its single-layered thickness(e.g., a thickness of one atom or one molecule constituting the firstcapping layer CL1).

In some example embodiments, as shown in FIG. 32, the magnetic layerMGL, the first capping layer CL1, and the second capping layer CL2 mayremain in a substantially oxygen-free state at this moment. Meanwhile, awafer may be exposed by an external atmosphere containing oxygen atoms,during its transferring and/or waiting procedures to be performedoutside a deposition chamber. Accordingly, an uppermost layer on thewafer may have a specific oxygen content (hereinafter, nature oxygencontent) originated from diffusion of oxygen atoms. According to exampleembodiments of inventive concepts, at this moment, the magnetic layerMGL, the first capping layer CL1, and the second capping layer CL2 mayhave oxygen contents less than or equivalent to the nature oxygencontent.

An oxygen treatment may be performed on the second capping layer CL2 (inS40). The oxygen treatment S40 may be performed to oxidize at least aportion of an exposed surface of the second capping layer CL2. Forexample, the oxygen treatment S40 may include supplying a gas containingoxygen at a temperature of 0 to 500 Celsius degree and a pressure ofabout 0.1 mT to about 1 T. In some example embodiments, the gas suppliedin the oxygen treatment S40 may include at least one of oxygen and ozonegases.

As the result of the oxygen treatment S40, as shown in FIG. 32, thesecond capping layer CL2 may have an increased oxygen content, comparedwith the case of S30. For example, the oxidized portion of the secondcapping layer CL2 may be an oxygen-containing noble metal layer or anoxygen-containing copper layer. In some example embodiments, the oxygencontent of the oxidized second capping layer CL2 may exhibit adecreasing trend from its exposed surface (e.g., a top surface) to themagnetic layer MGL, but example embodiments of inventive concepts neednot be limited thereto. For example, the oxygen content in the secondcapping layer CL2 may exhibit a variety of spatial distributions,depending on process conditions in the oxygen treatment S40 and/or amaterial or structure of the second capping layer CL2.

In some example embodiments, after the oxygen treatment S40, the secondcapping layer CL2 may include a stoichiometric oxide layer. For example,the second capping layer CL2 may be a ruthenium layer before performingthe oxygen treatment S40 but may include a ruthenium oxide layer afterperforming the oxygen treatment S40. In other example embodiments, afterperforming the oxygen treatment S40, the second capping layer CL2 mayinclude a non-stoichiometric oxide layer. For example, the secondcapping layer CL2 may include at least a portion, whose oxygen contentis greater or less than that of the stoichiometric oxide layer.

In still other example embodiments, after the oxygen treatment S40,oxygen atoms may be inhomogeneously distributed in the second cappinglayer CL2. That is, the second capping layer CL2 may include a firstportion and a second portion having an oxygen content greater than thefirst portion. For example, as exemplarily shown in FIG. 32, the oxygencontent of the oxidized second capping layer CL2 may exhibit adecreasing trend from its exposed surface (e.g., the top surface) to themagnetic layer MGL. Alternatively, after the oxygen treatment S40,oxygen atoms may be homogeneously distributed in the second cappinglayer CL2.

In some modified example embodiments, when the oxygen treatment S40 isnot performed, the second capping layer CL2 may be a material having anoxygen affinity less than the first capping layer CL1 and an oxygencontent greater than the first capping layer CL1. For example, thesecond capping layer CL2 may be formed to have an oxygen contentsubstantially greater than the nature oxygen content. In exampleembodiments, the oxygen treatment S40 may be omitted.

In other modified example embodiments, when the oxygen treatment S40 isnot performed, the first capping layer CL1 may be formed to have anoxygen content substantially greater than the nature oxygen content. Forexample, the formation of the first capping layer CL1 may includeforming the first capping layer CL1 under an oxygen containing ambient.

In still other modified example embodiments, before the formation of thesecond capping layer CL2, an oxidation process may be performed tooxidize at least a portion of an exposed surface of the first cappinglayer CL1. In example embodiments, the oxygen treatment S40 may beomitted.

Referring back to FIG. 31, a third capping layer CL3, for example, a topor bottom electrode, or extra layer, may be formed after the oxygentreatment S40 (in S50). The third capping layer CL3 may be formed of aconductive material. In some example embodiments, the third cappinglayer CL3 may be formed of a conductive material having an oxygenaffinity less than or equivalent to that of the second capping layerCL2, on which the oxygen treatment S40 is not yet performed, but exampleembodiments of inventive concepts need not be limited thereto. Forexample, in other embodiments, the third capping layer CL3 may be formedof a conductive material having an oxygen affinity greater than that ofthe second capping layer CL2, on which the oxygen treatment S40 is notyet performed.

A thermal treatment, for example, annealing, may be performed on theresultant structure provided with the third capping layer CL3 (in S60).In some example embodiments, the thermal treatment S60 may be performedat a temperature of 0 to 500 Celsius degree and a pressure of about 0.1mT to about 1 T for a duration of about 1 sec to about 10000 sec. Insome example embodiments, in the thermal treatment S60, at least one ofnitrogen or inert gases may be supplied as an ambient gas. However, butexample embodiments of inventive concepts need not be limited thereto.For example, process conditions for the thermal treatment S60 may bevariously modified depending on materials, structures and oxygencontents of the first and second capping layers CL1 and CL2.

During the thermal treatment S60, oxygen atoms in the second cappinglayer CL2 may be downward diffused to oxidize metal atoms of the firstcapping layer CL1. For example, metal atoms of the first capping layerCL1 may react with the oxygen atoms, which are supplied from the secondcapping layer CL2 during the thermal treatment S60, and form a metaloxide layer. In some example embodiments, as shown in FIG. 32, an oxygencontent of the first capping layer CL1 may be higher at a surfaceadjacent to the second capping layer CL2 than at a surface adjacent tothe magnetic layer MGL. This difference in oxygen content may resultfrom the fact that most oxygen atoms in the first capping layer CL1 areoriginated from the diffusion of the oxygen atoms in the second cappinglayer CL2.

In some modified example embodiments, the formation of the third cappinglayer CL3 may be omitted. For example, the thermal treatment S60 may beperformed after or during the oxygen treatment S40. In other modifiedexample embodiments, the formation of the third capping layer CL3 may beperformed after the thermal treatment S60.

According to example embodiments described with reference to FIGS. 31and 32, the magnetic layer MGL, the first capping layer CL1, and thesecond capping layer CL2 may serve as the magnetic layer MGL, theperpendicular magnetization inducing layer PMI, and the perpendicularmagnetization preserving layer PMP, respectively, in extrinsicperpendicular magnetization structures EPMSs described above.

FIG. 33 is a flowchart exemplarily illustrating a method of fabricatinga MTJ according to other embodiments of inventive concepts, and FIG. 34is a graph illustrating some aspects of the MTJ fabricated by the methodof FIG. 33. In more detail, FIG. 34 shows a temporal change in oxygencontent in layers constituting the MTJ, and the horizontal and verticalaxes represent the layer and the oxygen content, respectively. In orderto reduce complexity in the drawings and to provide better understandingof example embodiments of inventive concepts, FIG. 34 shows togetheroxygen contents in some steps described with reference to FIG. 33.

Referring to FIGS. 33 and 34, a first seed layer SL1, for example, a topor bottom electrode or an extra layer, and a second seed layer SL2, forexample, a perpendicular magnetization preserving layer PMP, may besequentially formed (in S15 and S25). The first seed layer SL1 may beformed of a conductive material, and the second seed layer SL2 may beformed of a material having an oxygen affinity less than tantalum. Forexample, the second seed layer SL2 may be formed of at least one ofnoble metals (e.g., ruthenium (Ru), rhodium (Rh), palladium (Pd), silver(Ag), osmium (Os), iridium (Ir), platinum (Pt), or gold (Au)) or copper.In some example embodiments, the first seed layer SL1 may be formed of aconductive material having an oxygen affinity less than or equivalent tothe second seed layer SL2. But example embodiments of inventive conceptsneed not be limited thereto. For example, in other example embodiments,the first seed layer SL1 may be formed of a material having an oxygenaffinity greater than the second seed layer SL2. In other exampleembodiments, the formation of the first seed layer SL1 may be omitted.

An oxygen treatment may be performed on the second seed layer SL2 (inS35). The oxygen treatment S35 may be performed to oxidize at least aportion of an exposed surface of the second seed layer SL2. For example,the oxygen treatment S35 may include supplying a gas containing oxygenat a temperature of 0 to 500 Celsius degree and/or a pressure of about0.1 mT to about 1 T. In some example embodiments, the gas supplied inthe oxygen treatment S35 may include at least one of oxygen and ozonegases.

As the result of the oxygen treatment S35, as shown in FIG. 34, thesecond seed layer SL2 may have an increased oxygen content, compared thecase of S25. For example, the oxidized portion of the second seed layerSL2 may be an oxygen-containing noble metal layer or anoxygen-containing copper layer. In some example embodiments, the oxygencontent of the oxidized second seed layer SL2 may exhibit a decreasingtrend from its exposed surface (e.g., a top surface) to the first seedlayer SL1, but example embodiments of inventive concepts need not belimited thereto. For example, the oxygen content in the second seedlayer SL2 may exhibit a variety of spatial distributions, depending onprocess conditions in the oxygen treatment S35 and/or a material orstructure of the second seed layer SL2.

In some example embodiments, after the oxygen treatment S35, the secondseed layer SL2 may include a stoichiometric oxide layer. For example,the second seed layer SL2 may be a ruthenium layer before performing theoxygen treatment S35 but may include a ruthenium oxide layer afterperforming the oxygen treatment S35. In other example embodiments, afterperforming the oxygen treatment S35, the second seed layer SL2 mayinclude a non-stoichiometric oxide layer. For example, after the oxygentreatment S35, the second seed layer SL2 may include at least a portion,whose oxygen content is greater or less than that of the stoichiometricoxide layer.

In still other example embodiments, after the oxygen treatment S35,oxygen atoms may be inhomogeneously distributed in the second seed layerSL2. That is, the second seed layer SL2 may include a first portion anda second portion having an oxygen content greater than the firstportion. For example, as exemplarily shown in FIG. 34, the oxygencontent of the oxidized second seed layer SL2 may exhibit a decreasingtrend from its exposed surface (e.g., the top surface) to the first seedlayer SL1. Alternatively, after the oxygen treatment S35, oxygen atomsmay be substantially homogeneously distributed in the second seed layerSL2.

Referring back to FIG. 33, a third seed layer SL3, for example, aperpendicular magnetization inducing layer PMI, and a magnetic layer MGLmay be sequentially formed after the oxygen treatment S35 (in S45 andS55). The third seed layer SL3 may be formed of a material having anoxygen affinity greater than the magnetic layer MGL and/or the secondseed layer SL2. In some example embodiments, the magnetic layer MGL maybe formed of a ferromagnetic material or the IPM layer, and the thirdseed layer SL3 may be formed of a metal layer an oxygen affinity greaterthan the second seed layer SL2. For example, the third seed layer SL3may be formed of at least one of magnesium, tantalum, titanium,aluminum, magnesium zinc, hafnium, or magnesium boron. In some exampleembodiments, the third seed layer SL3 may be formed to have a thicknessone to three times greater than its single-layered thickness (e.g., athickness of one atom or one molecule constituting the third seed layerSL3).

In some example embodiments, when the oxygen treatment S35 is notperformed, the second seed layer SL2 may be a material having an oxygenaffinity less than the third seed layer SL3 and an oxygen contentgreater than the third seed layer SL3. For example, the second seedlayer SL2 may be formed to have an oxygen content substantially greaterthan the nature oxygen content. In example embodiments, the oxygentreatment S35 may be omitted.

A thermal treatment may be performed on the resultant structure providedwith the magnetic layer MGL (in S65). In some example embodiments, thethermal treatment S65 may be performed at a temperature of 0 to 500Celsius degree and a pressure of about 0.1 mT to about 1 T for aduration of about 1 sec to about 10000 sec. In some example embodiments,in the thermal treatment S65, at least one of nitrogen or inert gasesmay be supplied as an ambient gas. Example embodiments of inventiveconcepts need not be limited thereto. For example, process conditionsfor the thermal treatment S65 may be variously modified depending onmaterials, structures and oxygen contents of the second and third seedlayers SL2 and SL3. In modified example embodiments, the thermaltreatment S65 may be performed between the formations of the magneticlayer MGL and the third seed layer SL3.

During the thermal treatment S65, oxygen atoms in the second seed layerSL2 may be upward diffused to oxidize metal atoms of the third seedlayer SL3. For example, metal atoms of the third seed layer SL3 mayreact with the oxygen atoms, which are supplied from the second seedlayer SL2 during the thermal treatment S65, and form a metal oxidelayer. In some example embodiments, as shown in FIG. 34, an oxygencontent of the third seed layer SL3 may be higher at a surface adjacentto the second seed layer SL2 than at a surface adjacent to the magneticlayer MGL. This difference in oxygen content may result from the factthat most oxygen atoms in the third seed layer SL3 are originated fromthe diffusion of the oxygen atoms in the second seed layer SL2.

According to example embodiments described with reference to FIGS. 33and 34, the magnetic layer MGL, the third seed layer SL3, and the secondseed layer SL2 may serve as the magnetic layer MGL, the perpendicularmagnetization inducing layer PMI, and the perpendicular magnetizationpreserving layer PMP, respectively, in extrinsic perpendicularmagnetization structures EPMSs described above.

FIG. 35 is an experimental graph exemplarily showing some magneticproperties of MTJ according to example embodiments of inventiveconcepts.

The experiment was performed on samples, in which the first upperstructure 301 including the EPM, PMI, and PMP layers 310, 320 and 330depicted in FIG. 18 was formed on the tunnel barrier 50 of magnesiumoxide (MgO). For all samples, the EPM and PMI layers 310 and 320 wereformed of CoFeB and MgO, respectively, while the PMP layer 330 wasformed of titanium for some of the samples and of ruthenium for theothers. In FIG. 35, curves C1 and C2 show results obtained from samplesincluding the PMP layers 330 of Ru and Ti, respectively. The remainingconditions of the experiment were substantially the same.

In graph, the horizontal axis represents an intensity of externallyapplied perpendicular magnetic field and the vertical axis represents aperpendicular magnetic moment measured from the EPM layer 310.

Referring to FIG. 35, for samples depicted by the curve C1, there was noremarkable difference in perpendicular magnetic moment between casesapplied with and without an external perpendicular magnetic field (e.g.,at 0 Oe and at 4000 Oe). By contrast, for other samples depicted by thecurve C2, the perpendicular magnetic moment was zero when an externalperpendicular magnetic field was not applied. From this result, it canbe said that the EPM layer 310 of Ru exhibits an improved perpendicularmagnetic moment property, compared with the case of titanium.

FIG. 36 is an experimental graph exemplarily showing other magneticproperties of MTJ according to example embodiments of inventiveconcepts.

Two types of samples were tested. Samples of the first type wereprepared to have the extrinsic perpendicular magnetization structureEPMS of FIG. 9 and other samples of the second type were prepared not tohave the extrinsic perpendicular magnetization structure EPMS. In moredetail, samples of the first type were fabricated to include layers ofCoFeB, MgO, and Ru, which were sequentially stacked on a magnesium oxidelayer provided as the tunnel barrier 50, and samples of the second typewere fabricated to include layers of CoFeB and Ta, which weresequentially stacked on a magnesium oxide layer provided as the tunnelbarrier 50.

In the experiment, from the samples of the first and second types,perpendicular anisotropy energy densities were measured with respect toa thickness of the magnetic layer (e.g., the CoFeB layer). In the graphof FIG. 36, horizontal and vertical axes represent a thickness and aperpendicular anisotropy energy density, respectively, of the magneticlayer, and curves C3 and C4 show results obtained from samples of thefirst and second types, respectively.

Referring to FIG. 36, the magnetic layer had positive perpendicularanisotropy energy densities, when it was formed to a thickness of 8, 10or 14 angstroms, as depicted by the curve C3. That is, for the extrinsicperpendicular magnetization structure EPMS of FIG. 9 or the samples ofthe first type, the magnetic layer exhibited perpendicular anisotropy ina specific thickness range t of approximately 3 angstroms toapproximately 17 angstroms. By contrast, as depicted by the curve C4,all samples of the second type had negative perpendicular anisotropyenergy densities, irrespective of their thicknesses. That is, themagnetic layer of the second structure did not exhibit the perpendicularanisotropic property.

FIGS. 37 and 38 are block diagrams schematically illustrating electronicdevices including a semiconductor device according to exampleembodiments of inventive concepts.

Referring to FIG. 37, an electronic device 1300 including asemiconductor device according to example embodiments of inventiveconcepts may be used in one of a personal digital assistant (PDA), alaptop computer, a mobile computer, a web tablet, a wireless phone, acell phone, a digital music player, a wire or wireless electronicdevice, or a complex electronic device including at least two onesthereof. The electronic device 1300 may include a controller 1310, aninput/output device 1320 such as a keypad, a keyboard, a display, amemory 1330, and a wireless interface 1340 that are combined to eachother through a bus 1350. The controller 1310 may include, for example,at least one microprocessor, a digital signal process, a microcontrolleror the like. The memory 1330 may be configured to store a command codeto be used by the controller 1310 or a user data. The memory 1330 mayinclude a semiconductor device according to example embodiments ofinventive concepts. The electronic device 1300 may use a wirelessinterface 1340 configured to transmit data to or receive data from awireless communication network using a RF signal. The wireless interface1340 may include, for example, an antenna, a wireless transceiver and soon. The electronic system 1300 may be used in a communication interfaceprotocol of a communication system such as CDMA, GSM, NADC, E-TDMA,WCDMA, CDMA2000, Wi-Fi, Muni Wi-Fi, Bluetooth, DECT, Wireless USB,Flash-OFDM, IEEE 802.20, GPRS, iBurst, WiBro, WiMAX, WiMAX-Advanced,UMTS-TDD, HSPA, EVDO, LTE-Advanced, MMDS, and so forth.

Referring to FIG. 38, a memory system including a semiconductor deviceaccording to example embodiments of inventive concepts will bedescribed. The memory system 1400 may include a memory device 1410 forstoring huge amounts of data and a memory controller 1420. The memorycontroller 1420 controls the memory device 1410 so as to read datastored in the memory device 1410 or to write data into the memory device1410 in response to a read/write request of a host 1430. The memorycontroller 1420 may include an address mapping table for mapping anaddress provided from the host 1430 (e.g., a mobile device or a computersystem) into a physical address of the memory device 1410. The memorydevice 1410 may be a semiconductor device according to exampleembodiments of inventive concepts.

The semiconductor memory devices disclosed above may be encapsulatedusing various and diverse packaging techniques. For example, thesemiconductor memory devices according to the aforementioned embodimentsmay be encapsulated using any one of a package on package (POP)technique, a ball grid arrays (BGAs) technique, a chip scale packages(CSPs) technique, a plastic leaded chip carrier (PLCC) technique, aplastic dual in-line package (PDIP) technique, a die in waffle packtechnique, a die in wafer form technique, a chip on board (COB)technique, a ceramic dual in-line package (CERDIP) technique, a plasticquad flat package (PQFP) technique, a thin quad flat package (TQFP)technique, a small outline package (SOIC) technique, a shrink smalloutline package (SSOP) technique, a thin small outline package (TSOP)technique, a thin quad flat package (TQFP) technique, a system inpackage (SIP) technique, a multi-chip package (MCP) technique, awafer-level fabricated package (WFP) technique and a wafer-levelprocessed stack package (WSP) technique.

The package in which the semiconductor memory device according to one ofthe above embodiments is mounted may further include at least onesemiconductor device (e.g., a controller and/or a logic device) thatcontrols the semiconductor memory device.

According to example embodiments of inventive concepts, a magnetictunnel junction may be configured to include an extrinsic perpendicularmagnetization structure having a magnetic layer, a perpendicularmagnetization preserving layer, and a perpendicular magnetizationinducing layer therebetween. The perpendicular magnetization preservinglayer may be formed of a material having a low oxygen affinity, and thisenables to prevent a perpendicular anisotropy in a magnetizationdirection of the magnetic layer from being deteriorated under thesubsequent thermal environments.

While example embodiments of inventive concepts have been particularlyshown and described, it will be understood by one of ordinary skill inthe art that variations in form and detail may be made therein withoutdeparting from the spirit and scope of the attached claims.

What is claimed is:
 1. A magnetic tunneling junction device comprising:a fixed magnetic structure; a free magnetic structure; and a tunnelbarrier between the fixed magnetic structure and the free magneticstructure, at least one of the fixed magnetic structure and the freemagnetic structure including a perpendicular magnetization preservinglayer, a magnetic layer between the perpendicular magnetizationpreserving layer and the tunnel barrier, and a perpendicularmagnetization inducing layer between the perpendicular magnetizationpreserving layer and the magnetic layer.
 2. The magnetic tunnelingjunction device of claim 1, wherein the magnetic layer is made of aferromagnetic material.
 3. The magnetic tunneling junction device ofclaim 2, wherein the ferromagnetic material is at least one of CoFeB,CoFe, NiFe, CoFePt, CoFePd, CoFeCr, CoFeTb, CoFeGd or CoFeNi.
 4. Themagnetic tunneling junction device of claim 1, wherein the magneticlayer has a thickness in a range of about 1 angstrom to about 30angstroms.
 5. The magnetic tunneling junction device of claim 4, whereinthe magnetic layer has a thickness in a range of about 3 angstroms toabout 17 angstroms.
 6. The magnetic tunneling junction device of claim1, wherein the perpendicular magnetization inducing layer is in directcontact with the magnetic layer.
 7. The magnetic tunneling junctiondevice of claim 1, wherein the perpendicular magnetization inducinglayer includes at least one of Ta, Ti, U, Ba, Zr, Al, Sr, Hf, La, Ce,Sm, Mg, Th, Ca, Sc, or Y.
 8. The magnetic tunneling junction device ofclaim 1, wherein the perpendicular magnetization inducing layer has anelectrical resistivity higher than the magnetic layer or theperpendicular magnetization preserving layer.
 9. The magnetic tunnelingjunction device of claim 1, wherein the perpendicular magnetizationinducing layer has a thickness less than the magnetic layer or theperpendicular magnetization preserving layer.
 10. The magnetic tunnelingjunction device of claim 1, wherein the perpendicular magnetizationpreserving layer has an electrical resistivity lower than theperpendicular magnetization inducing layer.
 11. The magnetic tunnelingjunction device of claim 1, wherein the perpendicular magnetizationpreserving layer is formed of at least one noble metal or copper. 12.The magnetic tunneling junction device of claim 11, wherein the at leastone noble metal includes ruthenium (Ru), rhodium (Rh), palladium (Pd),silver (Ag), osmium (Os), iridium (Ir), platinum (Pt), or gold (Au). 13.The magnetic tunneling junction device of claim 1, further comprising; asubstrate; wherein the fixed magnetic structure is a lower structurecloser to the substrate and the wherein the free magnetic structure isan upper structure further from the substrate.
 14. The magnetictunneling junction device of claim 1, further comprising; a substrate;wherein the free magnetic structure is a lower structure closer to thesubstrate and the wherein the fixed magnetic structure is an upperstructure further from the substrate.
 15. An electronic device,comprising: a bus; a wireless interface configured to transmit data toor receive data from a wireless communication network connected to thebus; an I/O device connected to the bus; a controller connected to thebus; and a memory including a semiconductor device including themagnetic tunneling junction device of claim 1, connected to the bus,configured to store a command code to be used by the controller or userdata.
 16. A memory system, comprising: a memory device including asemiconductor device including the magnetic tunneling junction device ofclaim 1, for storing data; and a memory controller configured to controlthe memory device to read data stored in the memory device or to writedata into the memory device in response to a read/write request of ahost.